title: Demonstration of Usutu virus antibodies in horses, Croatia.
abstract: We report the first serological evidence of Usutu virus (USUV) infection in horses in Croatia. During 2011, 1380 horse serum samples from healthy animals were collected from six northern Croatian counties. All samples were first screened for West Nile virus (WNV) immunoglobulin G (IgG) antibodies using an enzyme-linked immunosorbent assay (ELISA). Sixty-nine WNV ELISA-reactive samples were further tested for WNV antibodies by a virus neutralization assay (VN assay) and plaque reduction neutralization test (PRNT), and USUV by a VN assay and tick-borne encephalitis virus (TBEV) antibodies by PRNT. During the same period, 306 human serum samples from patients coming for routine testing with no symptoms of acute febrile disease were tested for USUV IgG using ELISA. Reactive samples were tested for both USUV and WNV using a VN assay. USUV-specific neutralizing antibodies were detected in two of 69 WNV ELISA-reactive horse serum samples. Seropositive animals were found in two different regions of Croatia. One additional sample showed specific WNV-neutralizing antibodies that cross-neutralized USUV. Only one human sample (0.3%) was reactive to USUV antibodies in an ELISA test. In a confirmatory test, WNV-neutralizing antibodies were detected, indicating cross-reactive antibodies with USUV in ELISA. The exposure to USUV was documented in two WNV ELISA-reactive horses at distant locations. These results indicate the presence of USUV in northern Croatia.
authors.affiliation: 1 Department of Microbiology and Infectious Diseases with Clinic, Faculty of Veterinary Medicine, University of Zagreb , Zagreb, Croatia .
authors.forename: Ljubo
authors.initials: L
authors.lastname: Barbic
authors.forename: Tatjana
authors.initials: T
authors.lastname: Vilibic-Cavlek
authors.forename: Eddy
authors.initials: E
authors.lastname: Listes
authors.forename: Vladimir
authors.initials: V
authors.lastname: Stevanovic
authors.forename: Ira
authors.initials: I
authors.lastname: Gjenero-Margan
authors.forename: Suncanica
authors.initials: S
authors.lastname: Ljubin-Sternak
authors.forename: Iva
authors.initials: I
authors.lastname: Pem-Novosel
authors.forename: Irena
authors.initials: I
authors.lastname: Listes
authors.forename: Gordana
authors.initials: G
authors.lastname: Mlinaric-Galinovic
authors.forename: Annapia
authors.initials: A
authors.lastname: Di Gennaro
authors.forename: Giovanni
authors.initials: G
authors.lastname: Savini
mesh_terms: D000818:Animals; D057134:Antibodies, Neutralizing; D000914:Antibodies, Viral / Q000097:blood*; D017523:Croatia / Q000453:epidemiology; D003429:Cross Reactions; D018349:Encephalitis Viruses, Japanese / Q000235:genetics / Q000276:immunology / Q000302:isolation & purification*; D004671:Encephalitis, Arbovirus / Q000453:epidemiology / Q000662:veterinary* / Q000821:virology; D004797:Enzyme-Linked Immunosorbent Assay / Q000662:veterinary; D018177:Flavivirus Infections / Q000453:epidemiology / Q000662:veterinary* / Q000821:virology; D006734:Horse Diseases / Q000453:epidemiology* / Q000821:virology; D006736:Horses; D006801:Humans; D009500:Neutralization Tests / Q000662:veterinary; D016036:Seroepidemiologic Studies; D014901:West Nile Fever / Q000453:epidemiology / Q000662:veterinary* / Q000821:virology; D014902:West Nile virus / Q000276:immunology / Q000302:isolation & purification
chemical_list: D057134:Antibodies, Neutralizing; D000914:Antibodies, Viral